Process control systems, like those used in chemical, petroleum, pharmaceutical, pulp and paper, and/or other manufacturing processes, typically include one or more process controllers communicatively coupled to at least one host (e.g., an operator workstation) and to one or more process control devices (e.g., field devices) configured to communicate via analog, digital or combined analog/digital communication signals and/or protocols. The field devices, which may be, for example, device controllers, valves, valve actuators, valve positioners, switches, transmitters (e.g., temperature, pressure, flow rate, and chemical composition sensors) and/or any combinations thereof, perform functions within the process control system such as opening and/or closing valves and measuring and/or inferring process parameters. A process controller receives signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices, uses this information to implement a control routine, and generates control signals that are sent over buses and/or other communication lines to the field devices to control the operation of the process control system.
The field devices may be communicatively coupled to the process controller(s) using two-wire interfaces in a point-to-point (e.g., one field device communicatively coupled to a field device bus) and/or a multi-drop (e.g., a plurality of field device communicatively coupled to a field device bus) wiring connection arrangements, and/or with wireless communications. Some field devices are configured to operate using relatively simple commands and/or communications (e.g., an ON command and an OFF command). Other more complex field devices may require more commands and/or more communication information, which may or may not include simple commands. For example, more complex field devices may communicate analog values with digital communications superimposed on the analog values using, for example, a Highway Addressable Remote Transducer (HART) communication protocol. Some field devices may use entirely digital communications (e.g., a FOUNDATION Fieldbus communication protocol).
In a process control system, each field device is typically coupled to a process controller via an input/output (I/O) card and/or I/O port of an I/O gateway, and a respective communication medium (e.g., a two-wire cable, a wireless link, and/or an optical fiber). Thus, a plurality of communication media are required to communicatively couple the plurality of field devices to the process controller(s). Often, the plurality of communication media coupled to the field devices are routed through one or more field junction boxes, at which point, the plurality of communication media are coupled to respective communication media (e.g., respective two-wire conductors) of a multi-conductor cable used to communicatively couple the field devices to the process controller(s) via one or more I/O cards.
Information from the field devices and/or the process controller(s) is usually made available over a data highway and/or communication network to one or more other hardware devices, such as operator workstations, personal computers, data historians, report generators, centralized databases, etc. Such devices are typically located in control rooms and/or other locations remotely situated relative to the harsher plant environment. These hardware devices, for example, run applications that enable an operator to perform any of a variety of functions with respect to the process(es) of a process plant, such as changing settings of the process control routine(s), modifying the operation of the control modules within the process controllers and/or the field devices, viewing the current state of the process(es), viewing alarms generated by field devices and/or controllers, simulating the operation of the process(es) for the purpose of training personnel and/or testing the process control software, maintaining and/or updating a configuration database, etc.
As an example, the DeltaV™ control system sold by Fisher-Rosemount Systems, Inc. an Emerson Process Management company supports multiple applications stored within and/or executed by different devices located at potentially diverse locations within a process plant. A configuration application, which resides in and/or is executed by one or more operator workstations, enables users to create and/or change process control modules, and/or download process control modules via a data highway and/or communication network to dedicated process controllers. Typically, these control modules are made up of communicatively coupled and/or interconnected function blocks that perform functions within the control scheme based on received inputs and/or that provide outputs to other function blocks within the control scheme. In addition to defining a control scheme, the configuration application also allows the configuration, allocation and/or definition of a specific I/O port and/or I/O channel for each field device. The I/O ports and/or I/O channels for field devices are subsequently configured into the process controllers and/or I/O gateways to facilitate communication between the process controllers and the field devices.
The configuration application may further allow a configuration engineer and/or operator to create and/or change operator interfaces that are used, for example, by a viewing application to display data to an operator and/or to enable the operator to change settings and/or parameters, such as set points, within the process control routines. Each process controller and, in some cases, field devices, stores and/or executes a controller application that runs the control modules assigned to implement actual process control functionality. The viewing applications, which may be run on, for example, one or more operator workstations, receive data from the controller application via the data highway, and/or display such data for process control system engineers, operators, or other users using user interfaces that may provide any of a number of different views, such as an operator's view, an engineer's view, a technician's view, etc. A data historian application is typically stored in and/or executed by a data historian device that collects and/or stores some or all of the data provided across the data highway. A configuration database application may run in yet another computer communicatively coupled to the data highway to store the current process control routine configuration(s) and/or data associated therewith. Alternatively, configuration application(s), viewing application(s), data historian application(s), configuration database(s) and/or configuration database application(s) may be located in and/or executed by any number of workstations including, for example, a single workstation.